Re: [PATCH] ARM: dts: bcm283x: Fix critical trip point

[Stefan Wahren <wahrenst@gmx.net>]

Am 09.12.19 um 19:17 schrieb Florian Fainelli:
> On 11/30/19 5:54 AM, Lukas Wunner wrote:
>> On Sat, Nov 30, 2019 at 01:31:13PM +0100, Stefan Wahren wrote:
>>> During definition of the CPU thermal zone of BCM283x SoC family there was
>>> a misunderstanding of the meaning "criticial trip point" and the thermal
>>> throttling range of the VideoCore firmware. The latter one takes effect
>>> when the core temperature is between 80 and 85 degree celsius. So the
>>> current critical trip point doesn't make sense, because the
>>> thermal shutdown appears before the firmware has a chance to throttle the
>>> ARM core(s).
>> FWIW, the thermal throttling range goes way above 85°C.
>>
>> At Kunbus we've performed numerous tests in a climate chamber
>> and my recollection is that a CM3 starts throttling above 80°C
>> with the frequency hovering between 600 and 1200 MHz.
>>
>> Once 85°C is reached, the frequency is fixed at 600 MHz.
>>
>> But there a additional tripping points above that when the frequency
>> gets further reduced to 400 MHz and later 300 MHz.
> Does that mean that you are okay with 90°C here, or would you rather see
> this be change to 85°C?

From my understanding the change is okay, but the wording in the patch
description is misleading.

Suggestion:

... The latter one takes effect when the core temperature is at least 85
degree celsius or higher.


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